This invention relates to a method for correcting the outputs of vehicle behavior sensors mounted in an electronic control unit of a vehicle control device mounted in a vehicle brake hydraulic pressure control system such as an antilock brake system (ABS), a traction control system (TRC) or an electronic stability control system (ESC), and such a vehicle control device in which are mounted vehicle behavior sensors of which the outputs have been corrected.
With sophistication of today's motor vehicles and for safer travel, an increasing number of today's motor vehicles are equipped with vehicle behavior sensors. Such vehicle behavior sensors detect the behavior of a vehicle in the travel direction of the vehicle, the direction transverse to the travel direction, the vertical direction and other directions. Based on signals from these sensors, the vehicle control device controls the brake hydraulic pressure so that the vehicle will travel safely and smoothly.
Such vehicle behavior sensors include acceleration sensors, which detect accelerations in predetermined sensing directions (including gravity).
In order for such vehicle behavior sensors to accurately detect the behavior of the vehicle, it is essential that the sensing direction of each sensor coincide with the direction in which it is desired to detect the behavior of the vehicle, such as the travel direction of the vehicle (X-axis direction) or the direction transverse to the travel direction (Y-axis direction).
But practically, no matter how carefully such vehicle behavior sensors are mounted on a vehicle, it is difficult to arrange such sensors such that the sensing direction of each sensor precisely coincides with the intended direction of the vehicle. Especially if such vehicle behavior sensors are mounted e.g. in a vehicle control device of the above-described type, it is more difficult to position the sensors such that the sensing direction of each sensor precisely coincides with the intended direction of the vehicle than when mounting such sensors directly on the vehicle frame.
In order to overcome this difficulty, JP patent publication 2004-506572 proposes to apply accelerations and pivoting motions to a vehicle control device of the above-described type which carries vehicle behavior sensors, compare the outputs of the respective sensors based on such accelerations or pivoting motions with theoretical output values which the respective sensors are supposed to produce if the sensors are positioned precisely as required, and correct the outputs of the sensors based on the difference between the actual outputs of the sensors and the theoretical values.
However, vehicle behavior sensors are ordinarily mounted in an onboard device such as a vehicle control device, and then the onboard device is mounted on a vehicle. Thus, while the method disclosed in the above publication can correct the outputs of the sensors when the sensors are mounted in the onboard device, the method cannot correct the outputs of the sensors with the onboard device mounted on the vehicle. The theoretical values are not clearly defined, either. Also, this publication fails to consider gain errors inherent to respective sensors.
The outputs of conventional vehicle behavior sensors were therefore not sufficiently reliable and more accurate vehicle behavior sensors are desired.
An object of the present invention is to more accurately detect the behavior of a vehicle.